<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>

    <style>
        .c1 {
            background-color: red;
        }
        
        .c2 {
            background-color: green;
        }
        
        .c3 {
            background-color: blue;
        }
        /* grouping */
        
        .c1,
        .c2,
        .c3 {
            width: 200px;
            height: 100px;
            font-size: 32px;
        }
    </style>
</head>

<body>
    <!-- 需求： -->
    <!-- 1. 有3个div -->
    <!-- 2. 每个div的背景色不一样 -->
    <!-- 3. 每个div的字体大小一样 -->

    <!-- div[class="c$"]*3 -->
    <div class="c1">C1</div>
    <div class="c2">C2</div>
    <div class="c3">C3</div>
</body>

</html>